Re: [PATCH -v3 0/15] x86: Remove support for TSC-less and CX8-less CPUs

H. Peter Anvin
2026-01-07T03:57:53Z

On 2026-01-04 05:08, Borislav Petkov wrote:
> On Mon, Dec 15, 2025 at 02:55:27PM +0100, Ahmed S. Darwish wrote:
>> If it does, then we can also remove X86_FEATURE_CPUID from word 3:
>>
>> --- linux.orig/arch/x86/include/asm/cpufeatures.h
>> +++ linux/arch/x86/include/asm/cpufeatures.h
>> @@ -94,3 +94,3 @@
>> #define X86_FEATURE_NONSTOP_TSC ( 3*32+24) /* "nonstop_tsc" TSC does not stop in C states */
>> -#define X86_FEATURE_CPUID ( 3*32+25) /* "cpuid" CPU has CPUID instruction itself */
>> +/* Reserved ( 3*32+25) */
>
> s/Reserved/Free/
>
> so that it gets reused.
>

Please DON'T do this.

I have been cleaning up the boot code and it turns out that having this flag
available makes the error message generating code in the boot stub a lot nicer.

-hpa